SS-31 and MOTS-C are supplied strictly as laboratory research materials. They are not approved, intended or authorised for human consumption or any therapeutic use in this context. This article is written for qualified researchers and is not medical advice.
Two peptides, one organelle
Mitochondrial dysfunction is a common thread across cardiovascular, metabolic and ageing research, and the two peptides here are both aimed squarely at it — yet they could hardly be more different in how they work. SS-31 is a small synthetic tetrapeptide that physically concentrates inside the mitochondrion and props up its inner membrane. MOTS-C is a naturally occurring peptide the mitochondrion itself encodes, and it acts as a hormone-like messenger that reprogrammes cellular metabolism. One is a stabiliser; the other is a signaller. Put them side by side and the contrast is a useful lens on how "mitochondrial health" can be approached from structure or from signalling.
| SS-31 | MOTS-C | |
|---|---|---|
| Class / peptide type | Aromatic-cationic mitochondria-targeted peptide (synthetic) | Mitochondrial-derived peptide (mitokine) |
| Primary target / mechanism | Cardiolipin at the inner mitochondrial membrane; stabilises ETC supercomplexes | AMPK pathway activation; metabolic signalling |
| Structure / length | 4 amino acids (D-Arg-2′,6′-Dmt-Lys-Phe-NH₂) | 16 amino acids, encoded by mitochondrial 12S rRNA |
| Half-life | ~2 hours | Short (delivery-limited) |
| Main research focus | Barth syndrome, cardiovascular, mitochondrial myopathy, ageing muscle | Metabolic homeostasis, insulin sensitivity, exercise physiology, longevity |
| Regulatory status | Investigational — Phase 3 (Barth syndrome) | Experimental; no approved use, WADA-prohibited |
SS-31: the membrane stabiliser
SS-31 (also known as Elamipretide, Bendavia or MTP-131) is a synthetic aromatic-cationic tetrapeptide developed in the laboratory of Dr Hazel Szeto. Its defining feature is physical: the peptide concentrates roughly 1000-fold at the inner mitochondrial membrane through electrostatic interaction with cardiolipin, the signature phospholipid of that compartment. That degree of organelle selectivity is rare for a small molecule, and it is the whole point of the design.
Once localised, SS-31 stabilises the cardiolipin–cytochrome c interaction that organises electron transport chain Complex IV and the wider respiratory supercomplexes. In aged or stressed mitochondria, that stabilisation preserves supercomplex architecture, reduces electron leak — a major source of reactive oxygen species — and helps maintain ATP synthesis and membrane potential. The compound is in active Phase 3 development for Barth syndrome, with a preclinical record spanning cardiac ischaemia-reperfusion, heart failure and age-related muscle decline. Its half-life is short, on the order of two hours. Researchers sourcing material can buy SS-31 UK at research grade with a COA, and the full mechanism is set out on our SS-31 knowledgebase page.
MOTS-C: the metabolic signaller
MOTS-C works at the opposite level of the system. It is a 16-amino acid peptide encoded not by the nuclear genome but by the mitochondrial genome itself — specifically a short open reading frame within the 12S rRNA region — and was characterised in 2015 by Lee and colleagues in Cell Metabolism. It belongs to the emerging class of mitochondrial-derived peptides and is described as a "mitokine" because it acts with endocrine-like reach, released into circulation and signalling to distant tissues.
Its primary action is activation of AMP-activated protein kinase (AMPK), the cell's master energy sensor. Through AMPK, MOTS-C promotes GLUT4-mediated glucose uptake in skeletal muscle, increases fatty acid oxidation and suppresses de novo lipid synthesis. Under metabolic stress it translocates into the nucleus and modulates stress-response gene expression, and it upregulates mitochondrial biogenesis markers such as PGC-1α. Circulating MOTS-C rises with exercise and falls with age, which is why it sits at the centre of metabolic and longevity research and is often framed as an exercise mimetic. It remains experimental — there is no approved therapeutic use, clinical progress has been constrained by delivery and bioavailability, and it is prohibited under WADA as an AMPK activator. Qualified researchers can buy MOTS-C UK as a laboratory reagent, with the detail on our MOTS-C knowledgebase page.
What the differences mean in a research context
The cleanest way to hold these two apart is structure versus signalling. SS-31 does not instruct the cell to do anything new — it protects an existing structure, keeping the inner membrane and its respiratory machinery intact so that mitochondria that are already stressed can keep functioning. MOTS-C, by contrast, is an active message: it switches on a metabolic programme through AMPK, changing how the cell handles glucose, fat and stress. A structural intervention and a regulatory one address the same organelle by entirely separate routes.
That difference maps onto their biology of origin. SS-31 is a designed drug — a synthetic four-residue peptide optimised for one job, cardiolipin binding — which is why its research programme is disease-specific and centred on Barth syndrome and cardiac injury. MOTS-C is an endogenous signalling molecule the body already makes and modulates with exercise and age, which is why its literature leans toward whole-organism metabolism, insulin sensitivity and longevity. Their regulatory positions differ in kind too: SS-31 is a defined investigational compound advancing through Phase 3 trials, while MOTS-C is an experimental peptide with no approved use and an anti-doping prohibition attached.
For research purposes the two are complementary rather than competing. Because one stabilises mitochondrial hardware and the other tunes metabolic software, they are not substitutes — they answer different questions. Both remain strictly in vitro research reagents here, and neither profile establishes safety or efficacy in humans.
The bottom line
SS-31 stabilises the inner mitochondrial membrane by binding cardiolipin; MOTS-C activates AMPK to regulate metabolism. Membrane stabiliser versus metabolic signaller — same organelle, opposite mechanisms. For research-grade material, see our dedicated pages to buy SS-31 UK and buy MOTS-C UK, each ≥99% purity with a COA.